(for each dimension) by the number of invocations per work group times the work group index, As with the one-dimensional case, this index is determinedīy thinking of it as a global compute space (without the work groups), and can be computed Number of compute shader invocations in this example is then 20 * 9 = 180. The cell that is shaded in gray represents invocation (0, 1) within work group (2, 0). The space is divided into 20 work groups, four in the x direction and five in the y direction.Įach work group is then divided into nine invocations, three in the x direction and three in The following figure shows a representation of a two-dimensional compute space where Invocation in the global compute space, starting at zero on the left and counting from there. The global index is simply the index of each The local invocation index (1) that is 2 * 3 + 1 = 7.
#COMPUTE SHADERS OPENGL 4.3 PLUS#
Taking the product of work group (2) and index number of invocations per work group (3), plus The global index determines an invocations’s location within the global compute space, rather than just within the work group. We can also refer to that invocation with a global index o 7, by indexing the total number of invocations starting at zero. The grey shaded invocation is in work group 2, and within that work group, it is invocation 1 (the invocations are indexed starting at zero). In this case, we have 5*3 = 15 shader invocations. Work groups, and the thinner lines represent the invocations within each work group. Per work group could be represented as the following figure. Technically, it is always defined as a three-dimensional space, but any of the three dimensions can be defined with a size of one(1), which effectively removes the dimension.įor example, a one-dimensional compute space with five work groups and three invocations The compute space can be defined as a 1, 2 or 3 dimensional space. Shader invocations) and the local work group space (the invocations within a particular work We think of this in terms of the global compute space (all Each work group is then brokenĭown into a number of invocations.
![compute shaders opengl 4.3 compute shaders opengl 4.3](https://i.ytimg.com/vi/ycSOnGzbNO4/maxresdefault.jpg)
This space is divided into a number of work groups. The number of invocations of a compute shader is governed by the user-defined compute Invocations by defining the number of work groups, and the number of invocations within each It is not tied inĪny way to the number of vertices or fragments being rendered. The number of invocations of the compute shader is completely user defined. The only non-user-defined inputs to a compute shader are a set of variables that determine where the shader invocation is within its “space” of execution. Similarly, it provides its results by writing to the same or other objects. It gets its work by fetching data directly from memory using image access functions such as the image load/store operations, or via shader storage buffer objects.
![compute shaders opengl 4.3 compute shaders opengl 4.3](https://images.anandtech.com/doci/7867/OpenGL_ES_Next.png)
The only way to execute the compute shader is via the OpenGL commands glDispatchCompute or glDispatchComputeIndirect.Ĭompute shaders do not have any direct user-defined inputs and no outputs at all. In fact, when a compute shader is linked with vertex, fragment, or other shader stages, it is effectively inert when drawing commands are executed. It is not executed in response to rendering commands. The compute shader is not a traditional shader stage in the same sense as the fragment or vertex shader. Compute shaders are integrated directly within OpenGL, and therefore are more suitable for general computing tasks that are more closely related to graphics rendering. Although APIs such as OpenCL and CUDA are already available for general purpose computation on the GPU, they are completely separate from OpenGL. The compute shader is most useful for tasks that are not directly related to rendering, such as physical simulation.
#COMPUTE SHADERS OPENGL 4.3 SERIAL#
It provides the ability to leverage 利用 the GPU and its inherent parallelism for general computing tasks that might have previously been implemented in serial on the CPU.
![compute shaders opengl 4.3 compute shaders opengl 4.3](https://jvm-gaming.org/uploads/default/original/2X/6/6b16396f0efdaa61d99443ab31fa641f2d5e75a8.png)
Shader stage that can be used for arbitrary computation. Compute shaders were introduced into OpenGL with Version 4.3.